Interstitial brachytherapy is a promising local treatment technique for well contained primary tumors. The problems of radiation necrosis and peripheral recurrence remain unsolved, however. Hyperthermia has been shown to sensitize tumors to radiation, particularly when delivered aggressively concurrent with low dose rate brachytherapy. The research philosophy here is to introduce an effective adjuvant therapy (interstitial thermotherapy) which can increase the radiation response in tumor tissue more than in the surrounding normal tissues. It is anticipated that this thermal enhancement of radiation response in the tumor can lead to reductions in both the required radiation dose for cure as well as the overall complication rate. A 100 kHz Magnetic Induction System will be constructed for heating ferromagnetic seeds which can be inserted in the radiation implant catheters either before, during or after the radiation treatment. The research proposed is to study three-dimensional temperature distributions induced by arrays of ferromagnetic seeds in phantom and animal models. The degree of automatic internal temperature regulation possible with curie point ferromagnetic seed heating will be determined as well as the required number and spacing of temperature sensors to enable efficacious clinical use of this interstitial technique. The relative effectiveness and applicability of ferromagnetic seed heating will be compared to the present interstitial microwave antenna heating technology as a basis for determining future directions for development of hyperthermia equipment technology.